系统分类对偏振光谱指数的影响
The effect of systematics on polarized spectral indices
摘要：
我们研究四个特别明亮的偏振紧凑型天体（Tau A，室女座A，3C 273和天炉座A）在7年的WMAP天空图，了解潜在的系统学参与估计的前景光谱指数的目标。我们估计的光谱指数，偏振角，偏振分数和表观尺寸和形状的这些对象时，平滑到一个标称分辨率为1度半高宽。其次，我们计算光谱指数作为偏振方向的函数，α。由于这些物体近似为具有恒定偏振角的点源，因此在缺乏系统性的情况下，该函数应该是恒定的。然而，计算它的K-和Ka-波段WMAP数据，我们发现强烈的指数变化的所有四个来源。对于Tau A，我们发现α =30度时的光谱指数β =-2.59+-0.03，α =50度时的光谱指数β =-2.03+-0.01。另一方面，Ka和Q带之间的光谱指数被发现是稳定的。一个简单的椭圆高斯玩具模型与参数匹配的观察到的Tau A再现所观察到的信号，并表明，光谱指数是特别敏感的检测器偏振角。基于这些发现，我们首先得出结论，估计光谱指数与WMAP K波段偏振数据在1度尺度是不稳健的。其次，我们注意到，这些问题可能是关注的地面和亚轨道实验，使用WMAP的偏振测量的Tau A的增益和偏振角的校准。
英文摘要：
We study four particularly bright polarized compact objects (Tau A, Virgo A, 3C273 and Fornax A) in the 7-year WMAP sky maps, with the goal of understanding potential systematics involved in estimation of foreground spectral indices. We estimate the spectral index, the polarization angle, the polarization fraction and apparent size and shape of these objects when smoothed to a nominal resolution of 1 degree FWHM. Second, we compute the spectral index as a function of polarization orientation, alpha. Because these objects are approximately point sources with constant polarization angle, this function should be constant in the absence of systematics. However, computing it for the K- and Ka-band WMAP data we find strong index variations for all four sources. For Tau A, we find a spectral index beta=-2.59+-0.03 for alpha=30 degrees, and beta=-2.03+-0.01 for alpha=50 degrees. On the other hand, the spectral index between Ka and Q band is found to be stable. A simple elliptical Gaussian toy model with parameters matching those observed in Tau A reproduces the observed signal, and shows that the spectral index is in particular sensitive to the detector polarization angle. Based on these findings, we first conclude that estimation of spectral indices with the WMAP K-band polarization data at 1 degree scales is not robust. Second, we note that these issues may be of concern for ground-based and sub-orbital experiments that use the WMAP polarization measurements of Tau A for calibration of gain and polarization angles.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
